Field of the Invention
The field of the invention is the production of electrooptical components or modules, which typically have a receptacle, also called a plug-in bay, for the connection and optical coupling of suitable coupling partners, such as optical lines. As the coupling partners, other optical or electrooptical elements, for instance for the sake of galvanic separations, a further electrooptical module as well, are also conceivable. For converting electrical signals into optical signals, or for converting optical signals into electrical signals, such modules have electrooptical converters, which have a light-projecting region (transmitter) or light-sensitive region (receiver) that in the context of the present invention can also be called optically active zones. For high coupling efficiency when optical signals are fed into wave guides or output from them, not only the electrooptical transformation of the signals but also a precise coupling of the signal-diverting and/or signal delivering optical wave guide (coupling partner) are necessary. As the transmitter, in optical transmission technology, light-emitting diodes (LEDs) or horizontal-beam laser diodes are for instance employed. Because of their construction, such diodes often have a high aperture number, which for high-efficiency optical coupling requires the use of lenses.
The invention relates to a method for producing an electrooptical module in which the electrooptical converter is disposed in a predetermined position on a substrate, and in which the substrate together with the converter is at least partly embedded in a molded body of a moldable material, and the molded body has at least one functional surface serving the purpose of coupling with a coupling partner.
One such production method is known from Published, European Patent Application EP 0 053 482 A2. In the known production method, a substrate (lead frame) of the desired shape is stamped out from a metal sheet (such as a copper foil) first and then gold-coated. Next, the converter (in the case of a transmitter, a laser diode, for instance, or in the case of a receiver, a photo diode) is mounted on the substrate and contacted by way of bond wires and conductive paste for the sake of electrical triggering or signal connection. Next, the substrate together with the converter and optionally other trigger circuits are placed in half shells, which form an injection mold of the desired contour. A suitable transparent, heat-curable resin is placed in the injection mold, and under temperature and pressure, a molded body that imbeds the converter is created. The molded body has at least one functional surface of a predetermined contour serving the purpose of coupling with a coupling partner. The functional surface may for instance be a convex face of a lens serving to shape the beam between the converter and an optical wave guide to be coupled. However, the functional surface may instead or in addition be embodied as a stop face or alignment face for the coupling partner (such as an optical wave guide plug). The molded body is then placed in a housing with mechanical locking elements for the coupling partner.
The known production method includes two especially critical production steps namely, positioning the converter on the substrate, and positioning the substrate in the injection mold, on whose precision the coupling and outcoupling efficiency attainable with the electrooptical module depends. The Published, European Patent Application EP 0 053 482 A2 provides no further teachings in this respect.